Imaging optical system, projection type display device, and imaging apparatus

ABSTRACT

The imaging optical system forms a first intermediate image at a position conjugate to a magnification side imaging surface and a second intermediate image at a position closer to a reduction side than the first intermediate image on an optical path and conjugate to the first intermediate image. The imaging optical system consists of a first optical system, a second optical system, and a third optical system in order from the magnification side to the reduction side along the optical path. The imaging optical system does not include a reflective member having a power.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. § 119 toJapanese Patent Application No. 2019-158528, filed on Aug. 30, 2019. Theabove application is hereby expressly incorporated by reference, in itsentirety, into the present application.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The technology of the present disclosure relates to an imaging opticalsystem, a projection type display device, and an imaging apparatus.

2. Description of the Related Art

In the related art, a projection type display device that enlarges andprojects an image, which is displayed on a light valve such as a liquidcrystal display device or a digital micromirror device (DMD, registeredtrademark), on a screen or the like has been widely used. As opticalsystems applicable to a projection type display device, for example, theoptical systems described in JP2017-211477A, WO2014/103324A, andWO2016/068269A are known.

JP2017-211477A discloses an imaging optical system capable of projectingan image displayed on an image display element disposed on a reductionside conjugate plane as an enlarged image on a magnification sideconjugate plane. The imaging optical system substantially consists of afirst optical system and a second optical system in order from themagnification side. The imaging optical system is configured such thatthe second optical system forms an image on the image display element asan intermediate image and the first optical system forms themagnification side intermediate image conjugate plane.

WO2014/103324A and WO2016/068269A disclose a system configured toperform projection from a first imaging surface on a reduction side to asecond imaging surface on a magnification side so as to form twointermediate images and to include a reflective surface having apositive power at a position closer to the magnification side than themagnification side intermediate image of the two intermediate images.

SUMMARY OF THE INVENTION

Projection type display devices are required to have a wide angle ofview, and in recent years, are also required to be able to supportlarger image display elements. The imaging optical system disclosed inJP2017-211477A has a configuration in which an intermediate image isformed only once. Therefore, in a case where the configuration isapplied to a larger image display element, the diameter of the lensclosest to the magnification side is large, which makes manufacturingdifficult. In addition, the size of the device is increased.

In the systems of WO2014/103324A and WO2016/068269A, since a reflectivesurface having a power is disposed to be closer to the magnificationside than the magnification side intermediate image, the rays near theoptical axis cannot reach the screen and cannot be used for imaging Thatis, there is a disadvantage in that half or more of the image circleincluding the vicinity of the optical axis cannot be used.

The present disclosure has been made in view of the above circumstances,and has an object to provide an imaging optical system which is capableof using a wide area of an image circle including the vicinity of theoptical axis and has favorable optical performance by keeping a lensdiameter small while having a wide angle of view, a projection typedisplay device including the imaging optical system, and an imagingapparatus including the imaging optical system.

According to an aspect of the technology of the present disclosure,there is provided an imaging optical system in which a magnificationside imaging surface and a reduction side imaging surface are conjugate,in which the imaging optical system forms a first intermediate image ata position conjugate to the magnification side imaging surface and asecond intermediate image at a position closer to a reduction side thanthe first intermediate image on an optical path and conjugate to thefirst intermediate image, in which the imaging optical system consistsof a first optical system, a second optical system, and a third opticalsystem in order from a magnification side to the reduction side alongthe optical path, in which magnification side surfaces of all lenses ofthe first optical system are located on the optical path to be closer tothe magnification side than the first intermediate image, in whichmagnification side surfaces of all lenses of the second optical systemare located on the optical path to be closer to the reduction side thanthe first intermediate image and to be closer to the magnification sidethan the second intermediate image, in which magnification side surfacesof all lenses of the third optical system are located on the opticalpath to be closer to the reduction side than the second intermediateimage, and in which the imaging optical system does not include areflective member having a power.

Assuming that a focal length of the first optical system is f1, acombined focal length of the first optical system and the second opticalsystem is f12, and a focal length of the imaging optical system is f, itis preferable that the imaging optical system of the above aspectsatisfies Conditional Expressions (1) and (2). Further, it is preferablethat the imaging optical system of the above aspect satisfiesConditional Expressions (1) and (2) and also satisfies at least one ofConditional Expressions (1-1) or (2-1).1<|f1/f|<5  (1)0.8<|f12/f|<3  (2)1.5<|f1/f|<3  (1-1)1<|f12/f|<2  (2-1)

Assuming that a back focal length of the imaging optical system on thereduction side is Bf and a focal length of the imaging optical system isf, the imaging optical system of the above aspect preferably satisfiesConditional Expression (3), and more preferably satisfies ConditionalExpression (3-1).5<|Bf/f|  (3)6<|Bf/f|<20  (3-1)

Assuming that a maximum image height on the reduction side imagingsurface is Ymax, and a focal length of the imaging optical system is f,the imaging optical system of the above aspect preferably satisfiesConditional Expression (4) and more preferably satisfies ConditionalExpression (4-1).1.9<|Y max/f|  (4)2.1<|Ymax/f|<3.2  (4-1)

In a case where a maximum image height on the reduction side imagingsurface is Ymax and a ray is incident from the reduction side imagingsurface to the imaging optical system at a height of Ymax from anoptical axis in parallel with an optical axis, assuming that an air gapin which the first intermediate image is located is a first air gap in acase where the first intermediate image is located inside the air gap,and an air gap which is adjacent to the magnification side of a lens inwhich the first intermediate image is located is the first air gap in acase where the first intermediate image is located inside the lens, anangle formed between a first extension line obtained by extending theray in the first air gap and the optical axis is θ, and a sign of θ isnegative in a case where a first intersection point, which is anintersection point between a first extension line and the optical axis,is located to be closer to the magnification side than the firstintermediate image, and the sign of θ is positive in a case where thefirst intersection point is located to be closer to the reduction sidethan the first intermediate image, where a unit of θ is degrees, theimaging optical system of the above aspect preferably satisfiesConditional Expression (5) and more preferably satisfies ConditionalExpression (5-1).−15<θ<15  (5)−13<θ<13  (5-1)

In a case where a maximum image height on the reduction side imagingsurface is Ymax and a ray is incident from the reduction side imagingsurface to the imaging optical system at a height of Ymax from anoptical axis in parallel with an optical axis, assuming that a height ofthe ray from the optical axis on a lens surface closest to themagnification side in the second optical system is h1, an air gap inwhich the first intermediate image is located is a first air gap in acase where the first intermediate image is located inside the air gap,and an air gap which is adjacent to the magnification side of a lens inwhich the first intermediate image is located is the first air gap in acase where the first intermediate image is located inside the lens, anintersection point between a first extension line obtained by extendingthe ray in the first air gap and the optical axis is a firstintersection point, a distance on the optical axis between the firstintersection point and the lens surface closest to the magnificationside in the second optical system is dd1, a height of the ray from theoptical axis on a lens surface closest to the magnification side in thethird optical system is h2, an air gap in which the second intermediateimage is located is a second air gap in a case where the secondintermediate image is located inside the air gap, and an air gap whichis adjacent to the magnification side of a lens in which the secondintermediate image is located is the second air gap in a case where thesecond intermediate image is located inside the lens, an intersectionpoint between a second extension line obtained by extending the ray inthe second air gap and the optical axis is a second intersection point,a distance on the optical axis between the second intersection point andthe lens surface closest to the magnification side in the third opticalsystem is dd2, and a larger value of |h1/dd1| and |h2/dd2| is hdA and asmaller value of |h1/dd1| and |h2/dd2| is hdB, it is preferable that theimaging optical system of the above aspect satisfies ConditionalExpressions (6) and (7).0.1<hdA<1  (6)0.03<hdB<0.3  (7)

In a case where an absolute value of a height of a principal ray havinga maximum angle of view from an optical axis is the maximum on a lenssurface closest to the magnification side in the first optical system,assuming that a distance on the optical axis from the lens surfaceclosest to the magnification side to a lens surface closest to thereduction side is TL, a maximum image height on the reduction sideimaging surface is Ymax, a height of the principal ray with the maximumangle of view from the optical axis on the lens surface closest to themagnification side is h, and a focal length of the imaging opticalsystem is f, the imaging optical system of the above aspect preferablysatisfies Conditional Expression (8), and more preferably satisfiesConditional Expression (8-1).20<(TL×Y max)/(|h|×|f|)<60  (8)30<(TL×Ymax)/(|h|×|f|)<50  (8-1)

Assuming that a focal length of the first optical system is f1, amaximum image height on the reduction side imaging surface is Ymax, aheight of the principal ray with the maximum angle of view from theoptical axis on the lens surface closest to the magnification side is h,and a focal length of the imaging optical system is f, the imagingoptical system of the above aspect preferably satisfies ConditionalExpression (9), and more preferably satisfies Conditional Expression(9-1).1.2<(f1×Y max²)/(|h|×f ²)<4  (9)1.5<(f1×Y max²)/(|h|×f ²)<3  (9-1)

It is preferable that all optical elements included in the imagingoptical system of the above aspect have a common optical axis.

The imaging optical system of the above aspect may be configured toinclude two or more optical path deflecting members that deflect theoptical path.

According to another aspect of the technology of the present disclosure,there is provided a projection type display device comprising: a lightvalve that outputs an optical image; and the imaging optical systemaccording to the above aspect, in which the imaging optical systemprojects the optical image, which is output from the light valve, on ascreen.

According to still another aspect of the technology of the presentdisclosure, there is provided an imaging apparatus comprising theimaging optical system according to the above aspect.

In the present specification, it should be noted that the terms“consisting of ˜” and “consists of ˜” mean that the lens may include notonly the above-mentioned elements but also lenses substantially havingno refractive powers, optical elements, which are not lenses, such as astop, a filter, and a cover glass, and mechanism parts such as a lensflange, a lens barrel, an imaging element, and a camera shakingcorrection mechanism.

The sign of the power and the surface shape of the lens including theaspheric surface will be considered in terms of the paraxial regionunless otherwise specified. The “focal length” used in the conditionalexpression is a paraxial focal length. The values used in ConditionalExpressions are values in a case where the d line is used as a referencein a state where the object at infinity is in focus unless otherwisespecified. The term “image circle” described herein means a maximumeffective image circle. The “d line”, “C line”, and “F line” describedherein are bright lines, the wavelength of the d line is 587.56 nm(nanometers), the wavelength of the C line is 656.27 nm (nanometers),and the wavelength of the F line is 486.13 nm (nanometers).

According to the technology of the present disclosure, it is possible toprovide an imaging optical system which is capable of using a wide areaof an image circle including the vicinity of the optical axis and hasfavorable optical performance by keeping a lens diameter small whilehaving a wide angle of view, a projection type display device includingthe imaging optical system, and an imaging apparatus including theimaging optical system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing a configuration and rays of animaging optical system according to an example of an embodiment relatingto the technology of the present disclosure corresponding to an imagingoptical system of Example 1 of the present disclosure.

FIG. 2 is a diagram showing an available area and an unavailable area ofan image circle in a system including a reflective member having apower, as a comparative example.

FIG. 3 is an enlarged view of a main part showing an example of a symbolin a conditional expression.

FIG. 4 is an enlarged view of a main part showing an example of a symbolin a conditional expression.

FIG. 5 is an aberration diagram of the imaging optical system accordingto Example 1 of the present disclosure.

FIG. 6 is a cross-sectional view showing a configuration and rays of animaging optical system according to Modification Example 1-1 of Example1 of the present disclosure.

FIG. 7 is a cross-sectional view showing a configuration and rays of animaging optical system according to Modification Example 1-2 of Example1 of the present disclosure.

FIG. 8 is a cross-sectional view showing a configuration and rays of animaging optical system according to Example 2 of the present disclosure.

FIG. 9 is an aberration diagram of the imaging optical system accordingto Example 2 of the present disclosure.

FIG. 10 is a cross-sectional view showing a configuration and rays of animaging optical system according to Modification Example 2-1 of Example2 of the present disclosure.

FIG. 11 is a cross-sectional view showing a configuration and rays of animaging optical system according to Example 3 of the present disclosure.

FIG. 12 is an aberration diagram of the imaging optical system accordingto Example 3 of the present disclosure.

FIG. 13 is a cross-sectional view showing a configuration and rays of animaging optical system according to Modification Example 3-1 of Example3 of the present disclosure.

FIG. 14 is a cross-sectional view showing a configuration and rays of animaging optical system according to Modification Example 3-2 of Example3 of the present disclosure.

FIG. 15 is a cross-sectional view showing a configuration and rays of animaging optical system according to Modification Example 3-3 of Example3 of the present disclosure.

FIG. 16 is a cross-sectional view showing a configuration and rays of animaging optical system according to Example 4 of the present disclosure.

FIG. 17 is an aberration diagram of the imaging optical system accordingto Example 4 of the present disclosure.

FIG. 18 is a cross-sectional view showing a configuration and rays of animaging optical system according to Modification Example 4-1 of Example4 of the present disclosure.

FIG. 19 is a schematic configuration diagram of a projection typedisplay device according to an embodiment of the present disclosure.

FIG. 20 is a schematic configuration diagram of a projection typedisplay device according to another embodiment of the presentdisclosure.

FIG. 21 is a schematic configuration diagram of a projection typedisplay device according to still another embodiment of the presentdisclosure.

FIG. 22 is a front perspective view of the imaging apparatus accordingto the embodiment of the present disclosure.

FIG. 23 is a rear perspective view of the imaging apparatus shown inFIG. 22.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an example of an embodiment according to the technology ofthe present disclosure will be described in detail with reference to thedrawings. FIG. 1 shows a configuration in a cross section including anoptical axis Z of an imaging optical system according to an embodimentof the present disclosure. The configuration example shown in FIG. 1corresponds to Example 1 described later. In FIG. 1, the left side isthe magnification side and the right side is the reduction side, and theon-axis rays 2 and the rays 3 with the maximum angle of view are alsoshown.

The imaging optical system according to the technology of the presentdisclosure may be a projection optical system mounted on a projectiontype display device, or may be an imaging optical system mounted on adigital camera or the like. Hereinafter, the imaging optical systemaccording to the technology of the present disclosure in a case wherethe imaging optical system is used for a projection optical system willbe described.

FIG. 1 shows an example in which an optical member PP is disposed on thereduction side of the imaging optical system, under the assumption thatthe imaging optical system is mounted on a projection type displaydevice. The optical member PP is a member such as various filters, acover glass, a color synthesis prism, or the like. The optical member PPis a member having no power, and a configuration in which the opticalmember PP is omitted is also possible.

FIG. 1 also shows a screen Scr and an image display surface Sim of alight valve, under the assumption that the imaging optical system ismounted on the projection type display device. In the projection typedisplay device, rays provided with image information on the imagedisplay surface Sim are incident on the imaging optical system throughthe optical member PP, and are projected on the screen Scr through theimaging optical system. In the following description, the “magnificationside” means the screen Scr side, and the “reduction side” means theimage display surface Sim side. The screen Scr is an example of the“magnification side imaging surface” of the present disclosure, and theimage display surface Sim is an example of the “reduction side imagingsurface” of the present disclosure. The imaging optical system has aneffect of making the magnification side imaging surface and thereduction side imaging surface conjugate.

The imaging optical system consists of, in order from the magnificationside to the reduction side along the optical path, a first opticalsystem G1, a second optical system G2, and a third optical system G3. Asan example, in the imaging optical system of FIG. 1, the first opticalsystem G1 consists of lenses L1 a to L1 f in order from themagnification side to the reduction side, the second optical system G2consists of the lenses L2 a to L2 k in order from the magnification sideto the reduction side, and the third optical system G3 consists oflenses L3 a to L3 g, an aperture stop St, and lenses L3 h to L3 n inorder from the magnification side to the reduction side.

The imaging optical system is a relay type optical system, and forms afirst intermediate image MI1 at a position conjugate to themagnification side imaging surface and a second intermediate image MI2at a position closer to a reduction side than the first intermediateimage MI1 on an optical path and conjugate to the first intermediateimage MI1. That is, the magnification side imaging surface, the firstintermediate image MI1, the second intermediate image MI2, and thereduction side imaging surface are all located to be conjugate.

The magnification side surfaces of all lenses of the first opticalsystem G1 are located on the optical path to be closer to themagnification side than the first intermediate image MI1. Themagnification side surfaces of all lenses of the second optical systemG2 are located on the optical path to be closer to the reduction sidethan the first intermediate image MI1 and to be closer to themagnification side than the second intermediate image MI2. Themagnification side surfaces of all lenses of the third optical system G3are located on the optical path to be closer to the reduction side thanthe second intermediate image MI2. That is, whether a certain lens isincluded in the first optical system G1 or the second optical system G2is determined by the positional relationship between the magnificationside surface of the lens and the first intermediate image MI1.Therefore, in a case where the first intermediate image MI1 is locatedinside a certain lens, the lens is included in the first optical systemG1 instead of the second optical system G2. However, the positionalrelationship between the magnification side surface of each lens andeach intermediate image is on the optical axis. For example, “themagnification side surfaces of all the lenses are located on the opticalpath to be closer to the magnification side than the first intermediateimage MI1” in the first optical system G1 means that the magnificationside surfaces of all the lenses of the first optical system G1 on theoptical axis is located on the optical path to be closer to themagnification side than the position of the first intermediate image MI1on the optical axis. The same configuration applies to the secondoptical system G2 and the third optical system G3. In addition, as forthe cemented lens, it is preferable that all the lenses in one cementedlens are included in the same optical system. Therefore, assuming thatthe surface closest to the magnification side in the cemented lens isthe “magnification side surface”, the “position” is considered.

In the example of FIG. 1, the first intermediate image MI1 is formedbetween the first optical system G1 and the second optical system G2,and the second intermediate image MI2 is formed between the secondoptical system G2 and the third optical system G3. In the firstintermediate image MI1 and the second intermediate image MI2 shown inFIG. 1, only a part including the vicinity of the optical axis is simplyindicated by a dotted line such that the position on the optical axis ofeach intermediate image can be understood. Thus, the images do notrepresent actual shapes.

The system for forming an intermediate image is able to suppress anincrease in the diameter of the magnification side lens while ensuring awide angle of view, and thus is suitable for use in a projection typedisplay device requiring a wide angle of view. In particular, ascompared with a system in which an intermediate image is formed onlyonce, in a system in which an intermediate image is formed twice, it iseasier to reduce the diameter of the magnification side lens whileensuring a wide angle of view. In addition, the number of locationswhere the rays separates at each image height increases. Thus, there isan advantage in correcting off-axis aberrations. Therefore, an imagingoptical system that forms an intermediate image twice has a wide angleof view and a large image circle while reducing the diameter of themagnification side lens. Thus, there is an advantage in realizing theoptical system in which the distortion and the field curvature aresatisfactorily corrected.

Further, the imaging optical system according to the technology of thepresent disclosure is configured not to include a reflective memberhaving a power, and therefore, rays near the optical axis can be usedfor forming an image on the screen Scr. This will be described withreference to a comparative example shown in FIG. 2. FIG. 2 is a diagramshowing an available area and an unavailable area in a case where animage display surface Sim is disposed in an image circle in a systemincluding a reflective surface having power as described inWO2014/103324A. In a system including a reflective surface having power,rays near the optical axis Z cannot be used. Therefore, as indicated bya hatched portion in FIG. 2, half or more of the image circle IC is anunavailable area in which the image display surface Sim cannot bedisposed. In this system, the image display surface Sim can be disposedonly in the area indicated by the outline in FIG. 2, and only a smallarea less than half of the image circle IC can be used.

On the other hand, since the imaging optical system according to thetechnology of the present disclosure does not include a reflectivemember having a power, rays near the optical axis can also be used, andhalf or more of the image circle including the optical axis portion canbe used. The imaging optical system in FIG. 1 is able to use the rays inthe entire area of the image circle, and the entire area of the imagecircle is an area which can be used for the image display surface Sim tobe disposed therein. Since the imaging optical system according to thetechnology of the present disclosure has such a high degree of designfreedom, the imaging optical system is also suitable for not only aconfiguration in which the center of the image display surface Sim is onthe optical axis, but also a configuration in which the center of theimage display surface Sim is disposed to be deviated from the opticalaxis Z.

Next, a preferred configuration of the imaging optical system accordingto the technology of the present disclosure will be described. In theimaging optical system, assuming that a focal length of the firstoptical system G1 is f1 and a focal length of the imaging optical systemis f, it is preferable that Conditional Expression (1) is satisfied.Conditional Expression (1) is an expression relating to the relaymagnification of the first intermediate image MI1. By not allowing theresult of Conditional Expression (1) to be equal to or less than thelower limit, it is easy to correct spherical aberration, fieldcurvature, and astigmatism. By not allowing the result of ConditionalExpression (1) to be equal to or greater than the upper limit, it iseasy to reduce the diameter of the lens near the first intermediateimage MI1. Further, in a case of the configuration satisfyingConditional Expression (1-1), more favorable characteristics can beobtained.1<|f1/f|<5  (1)1.5<|f1/f|<3  (1-1)

Further, in the imaging optical system, assuming that a combined focallength of the first optical system G1 and the second optical system G2is f12 and a focal length of the imaging optical system is f, it ispreferable that Conditional Expression (2) is satisfied. ConditionalExpression (2) is an expression relating to the relay magnification ofthe second intermediate image MI2. By not allowing the result ofConditional Expression (2) to be equal to or less than the lower limit,it is easy to correct spherical aberration, field curvature, andastigmatism. By not allowing the result of Conditional Expression (2) tobe equal to or greater than the upper limit, it is easy to reduce thediameter of the lens near the second intermediate image MI2. Further, ina case of the configuration satisfying Conditional Expression (2-1),more favorable characteristics can be obtained.0.8<|f12/f|<3  (2)1<|f12/f|<2  (2-1)

It is preferable that the imaging optical system satisfies ConditionalExpressions (1) and (2). Further, it is preferable to satisfy not onlyConditional Expressions (1) and (2) but also at least one of ConditionalExpressions (1-1) or (2-1).

In the imaging optical system, assuming that a back focal length of theimaging optical system on the reduction side is Bf and a focal length ofthe imaging optical system is f, it is preferable that ConditionalExpression (3) is satisfied. The “back focal length on the reductionside” is an air-equivalent distance on the optical axis from the lenssurface closest to the reduction side to the focal position on thereduction side of the imaging optical system. By not allowing the resultof Conditional Expression (3) to be equal to or less than the lowerlimit, it is possible to ensure a sufficient back focal length forinserting a color synthesis prism or the like used in the projectiontype display device. Further, it is preferable to satisfy ConditionalExpressions (3-1). By not allowing the result of Conditional Expression(3-1) to be equal to or less than the lower limit, a longer back focallength can be ensured. By not allowing the result of ConditionalExpression (3-1) to be equal to or greater than the upper limit,magnification of the optical system can be suppressed.5<|Bf/f|  (3)6<|Bf/f|<20  (3-1)

In the imaging optical system, assuming that the maximum image height onthe reduction side imaging surface is Ymax and the focal length of theimaging optical system is f, it is preferable that ConditionalExpression (4) is satisfied. By not allowing the result of ConditionalExpression (4) to be equal to or less than the lower limit, there is anadvantage in ensuring a wide angle of view. Further, it is preferable tosatisfy Conditional Expressions (4-1). By not allowing the result ofConditional Expression (4-1) to be equal to or less than the lowerlimit, there is an advantage in ensuring a wider angle of view. By notallowing the result of Conditional Expression (4-1) to be equal to orgreater than the upper limit, it is easy to perform aberrationcorrection while suppressing an increase in the diameter of the lens ofthe first optical system G1.1.9<|Ymax/f|  (4)2.1<|Ymax/f|<3.2  (4-1)

In the imaging optical system, assuming that the maximum image height onthe reduction side imaging surface is Ymax and the ray 3 c is incidentfrom the reduction side imaging surface to the imaging optical system,at a height of Ymax from the optical axis Z, in parallel with theoptical axis Z, it is preferable that θ described below satisfiesConditional Expression (5). FIG. 3 in which the imaging optical systemof FIG. 1 is partially enlarged shows an example of θ. θ is defined asfollows. The air gap in which the first intermediate image MI1 islocated is a first air gap. An angle formed between a first extensionline 4 shown by a two-dot chain line in FIG. 3 obtained by extending theray 3 c within the first air gap and the optical axis Z is θ. The unitof θ is degrees. The sign of θ is negative in a case where the firstintersection point P1, which is the intersection point of the firstextension line 4 and the optical axis Z, is located to be closer to themagnification side than the first intermediate image MIL and is positivein a case where the first intersection point P1 is located to be closerto the reduction side than the first intermediate image MI1. In theexample of FIG. 3, the first air gap is between the lens L1 f and thelens L2 a. In FIG. 3, reference numerals of some lenses are omitted toavoid complication of the drawing. It should be noted that the positionof the first intermediate image MI1 used here is the position of thefirst intermediate image MI1 on the optical axis. Further, unlike theexample of FIG. 3, in a case where the first intermediate image MI1 islocated inside the lens or on the surface of the lens, the air gapadjacent to the magnification side of the lens where the firstintermediate image MI1 is located is the first air gap.−15<θ<15  (5)−13<θ<13  (5-1)−10<θ<10  (5-2)

By not allowing the result of Conditional Expression (5) to be equal toor less than the lower limit, the first intermediate image MI1 isprevented from becoming excessively small, that is, the relaymagnification of the optical system in which the second optical systemG2 and the third optical system G3 are combined is prevented frombecoming excessively small. Thus, it is possible to reduce the load onthe magnification and performance of the first optical system G1 whileensuring the magnification of the entire imaging optical system. As aresult, the aberration correction in the first optical system G1 iseasy. If the aberration and the performance burden of the first opticalsystem G1 are large and the aberration is intended to be satisfactorilycorrected, the total length of the first optical system G1 is long, orthe distance from the lens surface closest to the magnification side inthe first optical system G1 to the magnification side pupil position ofthe first optical system G1 is long. As a result, the magnification sidelens is large in diameter. By not allowing the result of ConditionalExpression (5) to be equal to or greater than the upper limit, the firstintermediate image MI1 is prevented from becoming excessively large.Thus, the positive power given to the first optical system G1 for theconvergence of the ray may can be prevented from becoming excessivelystrong. In addition, there is an advantage in obtaining a wide angle ofview while suppressing an increase in the diameter of the lens closer tothe magnification side than the first intermediate image MI1. Further,in a case of the configuration satisfying Conditional Expression (5-1),more favorable characteristics can be obtained. In a case of theconfiguration satisfying Conditional Expression (5-2), more favorablecharacteristics can be obtained.

It is preferable that the imaging optical system satisfies ConditionalExpressions (4) and (5). Further, it is preferable to satisfy not onlyConditional Expressions (4) and (5) but also at least one of ConditionalExpressions (4-1), (5-1), or (5-2).

Further, in the imaging optical system, assuming that the maximum imageheight on the reduction side imaging surface is Ymax and the ray 3 c isincident from the reduction side imaging surface to the imaging opticalsystem, at a height of Ymax from the optical axis Z, in parallel withthe optical axis Z, it is preferable that |h1/dd1| described belowsatisfies Conditional Expression (10). FIG. 3 shows an example of h1 anddd1. h1 and dd1 are defined as follows. The height of the ray 3 c fromthe optical axis Z on the lens surface closest to the magnification sidein the second optical system G2 is h1. The distance on the optical axisbetween the first intersection point P1 defined in the description ofConditional Expression (5) and the lens surface of the second opticalsystem G2 closest to the magnification side is dd1.0.03<|h1/dd1|<1  (10)0.03<|h1/dd1|<0.85  (10-1)0.1<|h1/dd1|<0.85  (10-2)

By not allowing the result of Conditional Expression (10) to be equal toor less than the lower limit, a tilt angle of the ray 3 c near the firstintermediate image MI1 with respect to the optical axis Z is preventedfrom becoming excessively small. As a result, an increase in thediameter of the lens near the first intermediate image MI1 can besuppressed. By not allowing the result of Conditional Expression (10) tobe equal to or greater than the upper limit, the relay magnification ofthe optical system in which the second optical system G2 and the thirdoptical system G3 are combined is prevented from becoming excessivelysmall. Thus, it is possible to reduce the load on the magnification andperformance of the first optical system G1 while ensuring themagnification of the entire imaging optical system. As a result, it iseasy to perform the aberration correction in the first optical systemG1. If aberrations are intended to be satisfactorily corrected in a casewhere the magnification of the first optical system G1 increases, thediameter of the lens increases. Further, in a case of the configurationsatisfying Conditional Expression (10-1), more favorable characteristicscan be obtained. In a case of the configuration satisfying ConditionalExpression (10-2), more favorable characteristics can be obtained.

Further, in the imaging optical system, assuming that the maximum imageheight on the reduction side imaging surface is Ymax and the ray 3 c isincident from the reduction side imaging surface to the imaging opticalsystem, at a height of Ymax from the optical axis Z, in parallel withthe optical axis Z, it is preferable that |h2/dd2| described belowsatisfies Conditional Expression (11). FIG. 4 in which the imagingoptical system of FIG. 1 is partially enlarged shows an example of h2and dd2. h2 and dd2 are defined as follows. The height of the ray 3 cfrom the optical axis Z on the lens surface closest to the magnificationside in the third optical system G3 is h2. The air gap in which thesecond intermediate image MI2 is located is a second air gap. Theintersection point of the second extension line 5 shown by a two-dotchain line in FIG. 4 obtained by extending the ray 3 c within the secondair gap and the optical axis Z is a second intersection point P2. Thedistance on the optical axis between the second intersection point P2and the lens surface of the third optical system G3 closest to themagnification side is dd2. In the example of FIG. 4, the distancebetween the lens L2 k and the lens L3 a is the second air gap. In FIG.4, reference numerals of some lenses are omitted to avoid complicationof the drawing. It should be noted that the position of the secondintermediate image MI2 used here is the position of the secondintermediate image MI2 on the optical axis. Further, unlike the exampleof FIG. 4, in a case where the second intermediate image MI2 is locatedinside the lens or on the surface of the lens, the air gap adjacent tothe magnification side of the lens where the second intermediate imageMI2 is located is the second air gap.0.03<|h2/dd2|<1  (11)0.03<|h2/dd2|<0.85  (11-1)0.1<|h2/dd2|<0.85  (11-2)

By not allowing the result of Conditional Expression (11) to be equal toor less than the lower limit, a tilt angle of the ray 3 c near thesecond intermediate image MI2 with respect to the optical axis Z isprevented from becoming excessively small. As a result, an increase inthe diameter of the lens near the second intermediate image MI2 can besuppressed. By not allowing the result of Conditional Expression (11) tobe equal to or greater than the upper limit, the relay magnification ofthe third optical system G3 is prevented from becoming excessively smallThus, it is possible to reduce the load on the magnification andperformance of the optical system closer to the magnification side thanthe second intermediate image MI2 while ensuring the magnification ofthe entire imaging optical system. As a result, it is easy to performthe aberration correction in the optical system. If aberrations areintended to be satisfactorily corrected in a case where themagnification of the optical system closer to the magnification sidethan the second intermediate image MI2 increases, the diameter of thelens increases. Further, in a case of the configuration satisfyingConditional Expression (11-1), more favorable characteristics can beobtained. In a case of the configuration satisfying ConditionalExpression (11-2), more favorable characteristics can be obtained.

It is preferable that the imaging optical system satisfies ConditionalExpressions (10) and (11). Further, it is preferable to satisfy not onlyConditional Expressions (10) and (11) but also at least one ofConditional Expressions (10-1), (10-2), (11-1), or (11-2).

In the imaging optical system, assuming that the larger one of |h1/dd1|and |h2/dd2| is hdA and the smaller one is hdB, it is preferable thatConditional Expressions (6) and (7) are satisfied. In the examples shownin FIGS. 3 and 4, since |h1/dd1|=0.16 and |h2/dd2|=0.813, hdA=|h2/dd2|and hdB=|h1/dd1|.0.1<hdA<1  (6)0.1<hdA<0.85  (6-1)0.03<hdB<0.3  (7)0.1<hdB<0.3  (7-1)

In the case where hdA=|h2/dd2| and hdB=|h1/dd1|, by not allowing theresult of Conditional Expression (6) to be equal to or less than thelower limit, a tilt angle of the ray 3 c near the second intermediateimage MI2 with respect to the optical axis Z is prevented from becomingexcessively small. As a result, an increase in the diameter of the lensnear the second intermediate image MI2 can be suppressed. By notallowing the result of Conditional Expression (6) to be equal to orgreater than the upper limit, the relay magnification of the thirdoptical system G3 is prevented from becoming excessively small. Thus, itis possible to reduce the load on the magnification and performance ofthe optical system closer to the magnification side than the secondintermediate image MI2 while ensuring the magnification of the entireimaging optical system. As a result, it is easy to perform theaberration correction in the optical system. If aberrations are intendedto be satisfactorily corrected in a case where the magnification of theoptical system closer to the magnification side than the secondintermediate image MI2 increases, the diameter of the lens increases.Further, in a case of the configuration satisfying ConditionalExpression (6-1), more favorable characteristics can be obtained.

In the case where hdA=|h2/dd2| and hdB=|h1/dd1|, by not allowing theresult of Conditional Expression (7) to be equal to or less than thelower limit, a tilt angle of the ray 3 c near the first intermediateimage MI1 with respect to the optical axis Z is prevented from becomingexcessively small. As a result, an increase in the diameter of the lensnear the first intermediate image MI1 can be suppressed. By not allowingthe result of Conditional Expression (7) to be equal to or greater thanthe upper limit, the relay magnification of the optical system in whichthe second optical system G2 and the third optical system G3 arecombined is prevented from becoming excessively small. Thus, it ispossible to reduce the load on the magnification and performance of theoptical system closer to the magnification side than the firstintermediate image MI1 while ensuring the magnification of the entireimaging optical system. As a result, it is easy to perform theaberration correction in the optical system. If aberrations are intendedto be satisfactorily corrected in a case where the magnification of theoptical system closer to the magnification side than the firstintermediate image MI1 increases, the diameter of the lens increases.Further, in a case of the configuration satisfying ConditionalExpression (7-1), more favorable characteristics can be obtained. In acase where hdA=|h1/dd1| and hdB=|h2/dd2|, the effect of ConditionalExpression (6) and the effect of Conditional Expression (7) arereplaced.

It is preferable that the imaging optical system is configured to betelecentric on the reduction side. In a projection type display device,spectral characteristics of a color synthesis prism disposed between animaging optical system and a light valve change depending on an angle ofincident ray. It is desired that the imaging optical system used incombination with the member having the incident angle dependency isconfigured to be telecentric on the reduction side. Here, the term“telecentric” is not limited to a case where the inclination of theprincipal ray with respect to the optical axis Z is 0 degree, and anerror of ±3 degrees is allowed. In the imaging optical system of FIG. 1,the imaging optical system is configured to be telecentric on thereduction side, and the ray 3 c used in the above descriptioncorresponds to the principal ray with the maximum angle of view. Inaddition, unlike the example of FIG. 1, in a system that does notinclude an aperture stop, in a case where rays are viewed in a directionfrom the magnification side to the reduction side, the telecentricitymay be determined by using, as a substitute for the principal ray, thebisector of the highest ray on the upper side and the lowest ray on thelower side in the cross section of the rays condensed at an optionalpoint on the image display surface Sim that is the reduction sideimaging surface.

In the imaging optical system, it is preferable that an absolute valueof a height of the principal ray with the maximum angle of view from theoptical axis Z is the maximum on a lens surface closest to themagnification side in the first optical system G1. In addition to thisconfiguration, assuming that a distance on the optical axis from thelens surface closest to the magnification side to the lens surfaceclosest to the reduction side is TL, a maximum image height on thereduction side imaging surface is Ymax, a height of the principal raywith the maximum angle of view from the optical axis Z on the lenssurface closest to the magnification side is h, and a focal length ofthe imaging optical system is f, it is preferable that the imagingoptical system satisfies Conditional Expression (8). By not allowing theresult of Conditional Expression (8) to be equal to or less than thelower limit, there is an advantage in suppressing an increase in thediameter of the magnification side lens. By not allowing the result ofConditional Expression (8) to be equal to or greater than the upperlimit, there is an advantage in performing favorable aberrationcorrection, particularly correction of distortion and astigmatism whileobtaining a wide angle of view. Further, in a case of the configurationsatisfying Conditional Expression (8-1), more favorable characteristicscan be obtained.20<(TL×Ymax)/(|h|×|f|)<60  (8)30<(TL×Ymax)/(|h|×|f|)<50  (8-1)

In the imaging optical system, assuming that a focal length of the firstoptical system G1 is f1, a maximum image height on the reduction sideimaging surface is Ymax, a height of the principal ray with the maximumangle of view from the optical axis Z on the lens surface closest to themagnification side is h, and a focal length of the imaging opticalsystem is f, it is preferable to satisfy Conditional Expression (9). Bynot allowing the result of Conditional Expression (9) to be equal to orless than the lower limit, there is an advantage in suppressing anincrease in the diameter of the magnification side lens. By not allowingthe result of Conditional Expression (9) to be equal to or greater thanthe upper limit, there is an advantage in performing favorableaberration correction, particularly correction of distortion andastigmatism while obtaining a wide angle of view. Further, in a case ofthe configuration satisfying Conditional Expression (9-1), morefavorable characteristics can be obtained.1.2<(f1×Ymax²)/(|h|×f ²)<4  (9)1.5<(f1×Ymax²)/(|h|×f ²)<3  (9-1)

It is preferable that all the optical elements included in the imagingoptical system have the common optical axis Z. In this case, there is anadvantage in making the entire area of the image circle available, andthe cost can be reduced since the structure can be simplified.

Each optical system in the imaging optical system can be configured, forexample, as follows. The first optical system G1 may be configured tocomprise a negative meniscus lens closest to the magnification side. Insuch a case, there is an advantage in increasing the angle of view. Thefirst optical system G1 may be configured to comprise a plurality ofnegative meniscus lenses successively in order from the mostmagnification side. In such a case, there is an advantage in increasingthe angle of view. The lens closest to the reduction side in the firstoptical system G1 may be a positive lens. In such a case, there is anadvantage in reducing the diameter of the lens. The lens closest to themagnification side in the second optical system G2 may be a positivelens. In such a case, there is an advantage in reducing the diameter ofthe lens. The lens surface closest to the magnification side in thesecond optical system G2 may be a convex surface. In such a case, thereis an advantage in reducing the diameter of the lens. The lens closestto the reduction side in the third optical system G3 may be a positivelens. In such a case, there is an advantage in making the optical systemtelecentric on the reduction side.

The number of lenses included in each optical system may be differentfrom the number shown in FIG. 1. All the optical elements having powersincluded in the imaging optical system may be configured as lenses. Alllenses included in the imaging optical system preferably have arefractive index of 2.2 or less at the d line, and more preferably 2 orless in consideration of the availability of current lens materials. Theimaging optical system may be configured to include a diffractiveoptical surface. In a case where a diffractive optical surface isprovided on a surface of a certain lens, the technology of the presentdisclosure can be applied by regarding the diffractive optical surfaceas a lens surface for convenience. The imaging optical system preferablyhas a total angle of view greater than 120 degrees, more preferablygreater than 125 degrees, and even more preferably greater than 130degrees. The imaging optical system preferably has an F number of 3 orless. In the imaging optical system, it is preferable that distortion issuppressed within a range of −2% or more and +2% or less.

FIG. 1 shows an example of an imaging optical system having a straightoptical path, but the present disclosure is not limited to this. Theimaging optical system may be provided with an optical path deflectingmember that deflects the optical path so as to deflect the optical path.As the optical path deflecting member, for example, a member having areflective surface such as a mirror can be used. By deflecting theoptical path, a configuration advantageous for miniaturization can beobtained. For example, as in the imaging optical system shown in FIG. 6to be described later as a modification example, there may be provided afirst optical path deflecting member R1 that deflects the optical pathby 90 degrees and a second optical path deflecting member R2 thatdeflects the optical path by 90 degrees. Thereby, the optical path maybe configured to be deflected twice. The angle at which the optical pathis deflected is not limited to strict 90 degrees, and may be an angleincluding an error of ±3 degrees, for example. It is preferable that theangle of deflection is 90 degrees since the structure is simple in termsof assembling and manufacturing, but the angle is not necessarily 90degrees.

As a location where the optical path deflecting member is disposed, itis preferable to select an air gap formed such that the distance on theoptical axis between two lens surfaces adjacent to the optical pathdeflecting member on the magnification side and the reduction side ofthe optical path deflecting member is a length equal to or greater than60% of the effective diameter of the larger of the effective diametersof these two lens surfaces. By disposing the optical path deflectingmember at such a location, it is possible to deflect the optical path ina state where half or more of the area including the vicinity of theoptical axis in the image circle can be used. As a result, it ispossible to improve compactness and installability of the apparatus.More preferably, the optical path deflecting member is disposed in theair gap which is formed such that the distance on the optical axisbetween two lens surfaces adjacent to the optical path deflecting memberon the magnification side and the reduction side of the optical pathdeflecting member is longer than the larger effective diameter of theeffective diameters of these two lens surfaces. By disposing the opticalpath deflecting member at such a location, the optical path can bedeflected while keeping the state where the entire area of the imagecircle can be used. As a result, it is possible to further improvecompactness and installability of the apparatus.

In a case where there is a location suitable that deflects the opticalpath as described above, the number of deflections of the optical pathcan be optionally set in accordance with the number of the locations. Ina case where the number of deflections of the optical path is two, thedirections of both deflections of the optical path may be the same, orthe directions of the first deflection and the second deflection of theoptical path may be opposite to each other. In the example shown in FIG.6, the optical axis Z is located in the plane of the paper before andafter the deflecting of the optical path through the two optical pathdeflecting members. However, the present disclosure is not limited tothis. The optical path may be deflected in a direction perpendicular tothe plane of the paper. However, it is preferable that the direction inwhich the optical path is deflected is appropriately set inconsideration of the available area of the image circle.

The “magnification side” and “reduction side” according to thetechnology of the present disclosure are determined depending on theoptical path, and the same applies to an imaging optical system thatforms a deflected optical path. For example, in the imaging opticalsystem that forms a deflected optical path, the phrase “the lens A iscloser to the magnification side than the lens B” has the same meaningas the phrase “the lens A is on the optical path to be closer to themagnification side than the lens B”. Therefore, the term “˜closest tothe magnification side” in the imaging optical system that forms thedeflected optical path means that something is closest to themagnification side on the optical path in terms of arrangement order,and does not mean that the something is closest to the screen Scr interms of distance.

The above-described preferred configuration and possible configurationscan be optionally combined, and are preferably selectively adopted asappropriate according to required specifications. According to thepresent embodiment, it is possible to realize an imaging optical systemwhich is capable of using rays of a wide area of an image circleincluding the vicinity of the optical axis and has favorable opticalperformance by keeping a lens diameter small while having a wide angleof view.

Next, numerical examples of the imaging optical system according to thetechnology of the present disclosure will be described.

Example 1

FIG. 1 shows a cross-sectional view of a lens configuration and rays ofthe imaging optical system according to Example 1. The configuration andthe illustration method are as described above, and some redundant partsthereof will not be described. The imaging optical system according toExample 1 consists of a first optical system G1, a second optical systemG2, and a third optical system G3 in order from the magnification sideto the reduction side. The first optical system G1 consists of lenses L1a to L1 f in order from the magnification side to the reduction side.The second optical system G2 consists of lenses L2 a to L2 k in orderfrom the magnification side to the reduction side. The third opticalsystem G3 consists of lenses L3 a to L3 g, an aperture stop St, andlenses L3 h to L3 n in order from the magnification side to thereduction side. A first intermediate image MI1 is formed between thefirst optical system G1 and the second optical system G2, and a secondintermediate image MI2 is formed between the second optical system G2and the third optical system G3.

Regarding the imaging optical system of Example 1, Tables 1A and 1B showbasic lens data, Table 2 shows specification, and Table 3 shows theaspheric surface coefficients thereof. Here, the basic lens data isdivided into two tables, Table 1A and Table 1B, in order to avoidlengthening of one table. Table 1A shows the first optical system G1 andthe second optical system G2, and Table 1B shows the third opticalsystem G3 and the optical member PP. Tables 1A and 1B show valuesobtained in a case where the distance from the magnification sideimaging surface to the lens surface closest to the magnification side is1550.

In Tables 1A and 1B, the column of Sn shows surface numbers. The surfaceclosest to the magnification side is the first surface, and the surfacenumbers increase one by one toward the reduction side. The column of Rshows radii of curvature of the respective surfaces. The column of Dshows surface distances on the optical axis between the respectivesurfaces and the surfaces adjacent to the reduction side. Further, thecolumn of Nd shows refractive indexes of the respective components atthe d line, and the column of vd shows Abbe numbers of the respectivecomponents at the d line.

In Tables 1A and 1B, signs of radii of curvature of surface shapesconvex toward the magnification side are set to be positive, and signsof radii of curvature of surface shapes convex toward the reduction sideare set to be negative. In Table 1B, in a place of a surface number of asurface corresponding to the aperture stop St, the surface number and aterm of (St) are noted. A value at the bottom place of D in Table 1indicates a distance between the image display surface Sim and thesurface closest to the reduction side in the table.

Table 2 shows the absolute value of the focal length |f|, the F numberFNo., and the value of the maximum total angle of view 2ω, on a d linebasis. (°) in the place of 2ω indicates that the unit thereof is adegree.

In the basic lens data, the reference sign * is attached to surfacenumbers of aspheric surfaces, and numerical values of the paraxialradius of curvature are written into the column of the radius ofcurvature of the aspheric surface. In Table 3, the row of Sn showssurface numbers of the aspheric surfaces, and the rows of KA and Amshows numerical values of the aspheric surface coefficients for eachaspheric surface. m is an integer of 3 or more. For example, m=4, 6, 8,10 for the aspheric surfaces of Example 1. The “E±n” (n: an integer) innumerical values of the aspheric surface coefficients of Table 3indicates “×10±n”. KA and Am are the aspheric surface coefficients inthe aspheric surface expression represented by the following expression.Zd=C×H2/{1+(1−KA×C2×H2)½}+ΣAm×Hm

Here,

Zd is an aspheric surface depth (a length of a perpendicular from apoint on an aspheric surface at height H to a plane that isperpendicular to the optical axis and contacts with the vertex of theaspheric surface),

H is a height (a distance from the optical axis to the lens surface),

C is a paraxial curvature,

KA and Am are aspheric surface coefficients, and

Σ in the aspheric surface expression means the sum with respect to m.

In data of each table, a degree is used as a unit of an angle, and mm(millimeter) is used as a unit of a length, but appropriate differentunits may be used since the optical system can be used even in a casewhere the system is enlarged or reduced in proportion. Each of thefollowing tables shows numerical values rounded off to predetermineddecimal places.

TABLE 1A Example 1 Sn R D Nd νd 1 147.7946 10.7403 1.72916 54.68 244.7071 4.8034 *3 133.3356 5.8435 1.58573 59.70 *4 38.1485 34.1834 5132.4823 30.0007 1.80610 33.27 6 −135.1744 5.9796 7 −138.6883 29.99921.84666 23.78 8 225.1860 6.7570 9 −80.4586 14.9991 1.77250 49.60 10−37.9774 0.2001 11 323.9486 12.6694 1.77250 49.60 12 −111.0361 73.024413 104.3289 24.9992 1.80400 46.58 14 −473.5056 34.1860 15 −68.640425.0007 1.51742 52.43 16 104.6105 6.2112 17 216.2068 16.0801 1.8040046.58 18 −143.5173 50.0335 19 286.2820 12.3016 1.72916 54.68 20−181.1906 101.9231 21 166.2958 10.1691 1.49700 81.61 22 −99.7880 0.199123 70.0990 15.3975 1.60311 60.64 24 −69.6824 0.3780 25 −66.9256 1.80051.74000 28.30 26 48.6288 24.1060 27 −33.5706 1.7991 1.68893 31.07 28−43.7213 0.1991 29 178.0573 16.5633 1.59522 67.73 30 −100.4780 69.275831 101.4829 19.2790 1.80100 34.97 32 −1641.9796 0.1996 33 45.954216.0916 1.80610 33.27 34 61.4489 19.9997

TABLE 1B Example 1 Sn R D Nd νd 35 409.0962 8.1298 1.80518 25.42 3648.2416 10.9665 37 −192.0879 1.7991 1.80518 25.42 38 82.2784 19.9195 39−32.3837 2.9422 1.60562 43.71 40 −235.4556 5.0655 41 −94.9332 17.89681.80518 25.42 42 −48.7815 0.2006 43 513.9702 20.6740 1.77250 49.60 44−85.3754 0.2000 45 53.1373 20.0005 1.80400 46.58 46 1986.4668 1.2195 47−1350.6512 25.0009 1.67270 32.10 48 25.1241 28.4952 49(St) ∞ 2.3266 50−34.6262 8.1495 1.84666 23.78 51 96.9027 0.1006 52 89.2564 9.15301.49700 81.61 53 −40.9579 2.1969 54 64.9451 22.9578 1.49700 81.61 55−70.8361 0.2008 56 127.6592 13.1233 1.49700 81.61 57 −47.1138 0.6331 58−44.7589 2.2620 1.74950 35.33 59 79.6891 4.3197 60 662.8004 8.24561.49700 81.61 61 −88.5837 6.1239 62 160.3263 12.3154 1.89286 20.36 63−111.9534 34.0000 64 ∞ 61.8380 1.51633 64.14 65 ∞ 3.9696

TABLE 2 Example 1 |f| 11.32 FNo. 2.10 2ω(°) 133.0

TABLE 3 Example 1 Sn 3 4 KA 1.000000000000E+00 1.000000000000E+00 A49.002568559587E−06 7.969564472748E−06 A6 −3.654621931458E−09 2.033232540435E−09 A8 1.753195342563E−12 −8.742653059749E−13  A10−4.942672948841E−16  −2.950185751031E−15 

FIG. 5 shows aberration diagrams of the imaging optical system accordingto Example 1 in a case where the distance from the magnification sideimaging surface to the lens surface closest to the magnification side is1550. FIG. 5 shows, in order from the left, spherical aberration,astigmatism, distortion, and lateral chromatic aberration. In thespherical aberration diagram, aberrations at the d line, C line, and Fline are indicated by the solid line, the long dashed line, and theshort dashed line, respectively. In the astigmatism diagram, theaberration at the d line in the sagittal direction is indicated by asolid line, and the aberration at the d line in the tangential directionis indicated by the short dashed line. In the distortion diagram,aberration at the d line is indicated by the solid line. In the lateralchromatic aberration diagram, aberrations at the C line and the F lineare indicated by the long dashed line and the short dashed line,respectively. In the spherical aberration diagram, FNo. indicates an Fnumber. In the other aberration diagrams, to indicates a half angle ofview.

Symbols, meanings, description methods, and illustration methods of therespective data pieces according to Example 1 are the same as those inthe following examples unless otherwise noted. Therefore, in thefollowing description, repeated description will be omitted.

FIGS. 6 and 7 show examples, in which the optical path is deflected, asmodification examples of Example 1. The imaging optical system ofModification Example 1-1 shown in FIG. 6 is configured such two opticalpath deflecting members are added to the imaging optical system ofExample 1 so as to deflect the optical path twice. In the imagingoptical system of Modification 1-1, a first optical path deflectingmember R1, which deflects the optical path by 90 degrees, is disposed tobe closest to the reduction side in the first optical system G1, and asecond optical path deflecting member R2, which deflects the opticalpath by 90 degrees, is disposed inside the second optical system G2.

The imaging optical system of Modification Example 1-2 shown in FIG. 7is configured such that three optical path deflecting members are addedto the imaging optical system of Example 1 so as to deflect the opticalpath three times. In the imaging optical system of Modification Example1-2, a first optical path deflecting member R1, which deflects theoptical path by 90 degrees, is disposed to be closest to the reductionside in the first optical system G1, and a second optical pathdeflecting member R2, which deflects the optical path by 90 degrees, anda third optical path deflecting member R3, which deflects the opticalpath by 90 degrees, are disposed inside the second optical system G2.

Example 2

FIG. 8 shows a cross-sectional view of a lens configuration and rays ofthe imaging optical system according to Example 2. The imaging opticalsystem according to Example 2 consists of a first optical system G1, asecond optical system G2, and a third optical system G3 in order fromthe magnification side to the reduction side. The first optical systemG1 consists of lenses L1 a to L1 f in order from the magnification sideto the reduction side. The second optical system G2 consists of lensesL2 a to L2 k in order from the magnification side to the reduction side.The third optical system G3 consists of lenses L3 a to L3 e, an aperturestop St, and lenses L3 f to L3 k in order from the magnification side tothe reduction side. A first intermediate image MI1 is formed between thefirst optical system G1 and the second optical system G2, and a secondintermediate image MI2 is formed between the second optical system G2and the third optical system G3.

Regarding the imaging optical system of Example 2, Tables 4A and 4B showbasic lens data, Table 5 shows specification, Table 6 shows asphericsurface coefficients thereof, and FIG. 9 shows aberration diagrams.Table 4A, Table 4B, and FIG. 9 show data in a case where the distancefrom the magnification side imaging surface to the lens surface closestto the magnification side is 1240.

TABLE 4A Example 2 Sn R D Nd νd 1 110.0108 9.0653 1.79952 42.22 235.8446 4.8514 *3 153.0777 7.7445 1.58573 59.70 *4 28.2131 13.3733 577.0917 29.2470 1.80518 25.42 6 −205.6838 0.8240 7 734.2256 30.00091.84666 23.78 8 140.6855 5.4176 9 −48.9301 14.9991 1.80400 46.58 10−27.7925 0.1991 11 228.5134 11.1523 1.80400 46.58 12 −89.1338 50.1719 13100.2827 15.0009 1.80400 46.58 14 −347.9671 18.2872 15 −68.6332 25.00091.48749 70.24 16 90.4136 6.0677 17 207.7558 24.5838 1.80400 46.58 18−158.7402 43.9574 19 177.4103 10.9172 1.80400 46.58 20 −230.8068 87.508021 130.8111 7.5659 1.49700 81.61 22 −68.6306 0.1991 23 46.2773 11.43351.62041 60.29 24 −52.3695 0.3259 25 −49.6806 2.9844 1.69895 30.13 2629.1728 17.9692 27 −21.9108 1.7991 1.63980 34.47 28 −28.4264 0.2007 29119.2657 11.7135 1.59522 67.73 30 −75.7122 13.6272 31 73.6064 9.68851.65160 58.55 32 755.8900 14.6069 33 39.6778 18.8055 1.80400 46.58 3457.5965 20.0004

TABLE 4B Example 2 Sn R D Nd νd 35 −41.2495 8.7787 1.80518 25.42 36119.5109 11.5764 37 −30.7289 18.0009 1.80518 25.42 38 −37.2140 0.1997 39822.5438 25.0008 1.80400 46.58 40 −71.6238 0.1991 41 44.1462 14.40311.80400 46.58 42 240.1845 1.3997 43 480.6323 25.0005 1.60342 38.03 4420.0724 20.1133 45(St) ∞ 2.0999 46 −23.0813 12.6801 1.84666 23.78 47126.1208 0.2938 48 156.6799 9.2612 1.49700 81.61 49 −33.8103 0.2006 5098.4338 12.2403 1.49700 81.61 51 −47.2195 0.2000 52 63.5145 14.45391.53775 74.70 53 −50.3723 0.2882 54 −49.1451 22.7135 1.62004 36.26 5548.8188 11.2145 56 98.5649 10.4245 1.89286 20.36 57 −107.0048 27.2000 58∞ 49.4704 1.51633 64.14 59 ∞ 3.9794

TABLE 5 Example 2 |f| 9.05 FNo. 1.90 2ω(°) 132.8

TABLE 6 Example 2 Sn 3 4 KA 1.000000000000E+00 1.000000000000E+00 A41.795009521615E−05 1.692067099568E−05 A6 −1.206387019591E−08 1.283455322420E−08 A8 9.228349235864E−12 −1.290444635484E−11  A10−3.386182101615E−15  −3.569131609040E−14 

FIG. 10 shows an example, in which the optical path is deflected, as amodification example of Example 2. The imaging optical system ofModification Example 2-1 shown in FIG. 10 is configured such that twooptical path deflecting members are added to the imaging optical systemof Example 2 so as to deflect the optical path twice. In the imagingoptical system of Modification Example 2-1, a first optical pathdeflecting member R1, which deflects the optical path by 90 degrees, isdisposed to be closest to the reduction side in the first optical systemG1, and a second optical path deflecting member R2, which deflects theoptical path by 90 degrees, is disposed inside the second optical systemG2.

Example 3

FIG. 11 is a cross-sectional view of a lens configuration and rays ofthe imaging optical system according to Example 3. The imaging opticalsystem according to Example 3 consists of a first optical system G1, asecond optical system G2, and a third optical system G3 in order fromthe magnification side to the reduction side. The first optical systemG1 consists of lenses L1 a to L1 m in order from the magnification sideto the reduction side. The second optical system G2 consists of lensesL2 a to L2 g in order from the magnification side to the reduction side.The third optical system G3 consists of lenses L3 a to L3 e, an aperturestop St, and lenses L3 f to L3 h in order from the magnification side tothe reduction side. A first intermediate image MI1 is formed between thefirst optical system G1 and the second optical system G2, and a secondintermediate image MI2 is formed between the second optical system G2and the third optical system G3.

Regarding the imaging optical system of Example 3, Tables 7A and 7B showbasic lens data, Table 8 shows specification, Table 9 shows asphericsurface coefficients thereof, and FIG. 12 shows aberration diagrams.Table 7A, Table 7B, and FIG. 12 show data in the case where the distancefrom the magnification side imaging surface to the lens surface closestto the magnification is 752.7.

TABLE 7A Example 3 Sn R D Nd νd *1 −22.7843 5.6000 1.53158 55.08 *2−68.8174 3.3431 3 48.8035 1.8000 1.80518 25.45 4 23.7632 3.9001 534.3699 1.2500 1.83481 42.72 6 17.0998 6.1047 7 48.9982 1.1000 1.8040046.58 8 13.8324 10.7228 9 −29.7983 4.6993 1.48749 70.44 10 −53.16812.9867 11 −16.6862 7.9991 1.80400 46.58 12 −22.1270 2.5505 13 84.26284.4797 1.80518 25.45 14 −64.7206 48.0472 15 58.3901 13.6132 1.4970081.54 16 −30.3703 1.3000 1.84666 23.78 17 −59.1878 11.1667 18 2765.77811.2500 1.84666 23.78 19 31.5564 16.3416 1.49700 81.54 20 −44.7293 2.4799*21 −31.0853 3.4000 1.51007 56.24 *22 −25.9322 34.9993 23 46.7960 6.96861.80518 25.45 24 97.3830 112.7394

TABLE 7B Example 3 Sn R D Nd νd 25 44.8980 4.4354 1.80610 33.27 26839.7577 16.4661 27 30.4016 1.0000 1.84666 23.78 28 15.4624 12.01001.48749 70.44 29 31.2381 2.8305 30 86.8437 2.8840 1.80518 25.45 31−109.2009 1.9812 32 −21.2884 1.0000 1.80400 46.58 33 33.5958 8.23851.49700 81.54 34 −28.1427 6.9325 35 215.9032 9.0712 1.49700 81.54 36−27.4504 99.9996 37 −110.6783 5.7145 1.80400 46.58 38 −54.4489 51.029139 59.0752 7.0694 1.77250 49.60 40 571.2532 35.2280 41 39.5448 6.48231.65160 58.55 42 −57.3008 0.6032 43 −58.2157 1.5009 1.69895 30.13 4416.6240 0.2965 45 16.3633 5.7278 1.48749 70.44 46 491.9133 9.9226 47(St)∞ 23.0015 48 −73.8866 1.2006 1.69680 55.53 49 38.6457 8.2694 1.4970081.54 50 −32.4219 0.0991 51 87.1598 6.3766 1.80518 25.45 52 −55.058515.0000 53 ∞ 26.5000 1.51633 64.14 54 ∞ 0.0272

TABLE 8 Example 3 |f| 4.99 FNo. 2.40 2ω(°) 137.4

TABLE 9 Example 3 Sn 1 2 KA −5.597980971211E−01  −4.999999975361E+00  A32.510527488313E−03 3.511312067244E−03 A4 −1.901423833968E−04 −5.073029345472E−04  A5 7.051527070619E−06 3.974540261671E−05 A67.320901751491E−07 2.926027718482E−07 A7 −9.000228854029E−08 −2.248533865896E−07  A8 1.745592655144E−09 5.594011711523E−09 A91.877123657031E−10 7.632343116156E−10 A10 −9.445042960744E−12 −4.130878196081E−11  A11 −9.160768598151E−14  −7.475692751605E−13  A121.493926764218E−14 9.428499585636E−14 A13 −1.641905181353E−16 −7.266782652020E−16  A14 −1.063461588948E−17  −9.788147593542E−17  A152.565553020076E−19 2.139519194424E−18 A16 2.788561638688E−214.142815385452E−20 A17 −1.357808923286E−22  −1.668598940299E−21  A183.914311817552E−25 1.636063361795E−24 A19 2.579676897797E−264.470899908167E−25 A20 −2.415121388499E−28  −4.325012213072E−27  Sn 2122 KA −4.412426730387E−02  −5.000001485776E+00  A3 0.000000000000E+000.000000000000E+00 A4 1.236272319287E−06 −3.235177460791E−05  A51.308961841058E−06 1.010155737305E−06 A6 −9.703753150598E−08 1.902681194240E−07 A7 −7.530963486608E−09  −3.119941449663E−08  A89.245238660380E−10 1.562633441153E−09 A9 −2.678558217279E−12 7.225915475510E−11 A10 −2.507458899939E−12  −1.102175853423E−11  A115.386762800825E−14 1.916807594066E−13 A12 3.231219979512E−152.591030249581E−14 A13 −1.047614970529E−16  −1.149510133027E−15  A14−2.040188178055E−18  −2.185050991658E−17  A15 9.047059636809E−202.026604453705E−18 A16 4.936010295720E−22 −6.148676968192E−21  A17−3.738620671792E−23  −1.570948110067E−21  A18 5.073597545492E−261.927806181798E−23 A19 6.017302786605E−27 4.583452067695E−25 A20−3.123098946881E−29  −7.842909191608E−27 

FIGS. 13, 14, and 15 show examples, in which the optical path isdeflected, as modification examples of Example 3. The imaging opticalsystem of Modification Example 3-1 shown in FIG. 13 is configured suchthat two optical path deflecting members are added to the imagingoptical system of Example 3 so as to deflect the optical path twice. Inthe imaging optical system of Modification 3-1, a first optical pathdeflecting member R1, which deflects the optical path by 90 degrees, isdisposed to be closest to the magnification side in the second opticalsystem G2, and a second optical path deflecting member R2, whichdeflects the optical path by 90 degrees, is disposed to be closest tothe reduction side in the second optical system G2.

The imaging optical system of Modification Example 3-2 shown in FIG. 14is configured such that two optical path deflecting members are added tothe imaging optical system of Example 3 so as to deflect the opticalpath twice. In the imaging optical system of Modification 3-2, a firstoptical path deflecting member R1, which deflects the optical path by 90degrees, is disposed inside the first optical system G1, and a secondoptical path deflecting member R2, which deflects the optical path by 90degrees, is disposed to be closest to the magnification side in thesecond optical system G2.

The imaging optical system of Modification Example 3-3 shown in FIG. 15is configured such that four optical path deflecting members are addedto the imaging optical system of Example 3 so as to deflect the opticalpath four times. In the imaging optical system of Modification Example3-3, a first optical path deflecting member R1 that deflects the opticalpath by 90 degrees is disposed inside the first optical system G1, asecond optical path deflecting member R2 that deflects the optical pathby 90 degrees is disposed to be closest to the magnification side in thesecond optical system G2, a third optical path deflecting member R3 thatdeflects the optical path by 90 degrees is disposed to be closest to thereduction side in the second optical system G2, and a fourth opticalpath deflecting member R4 that deflects the optical path by 90 degreesis disposed inside the third optical system G3.

Example 4

FIG. 16 shows a cross-sectional view of a lens configuration and rays ofthe imaging optical system of Example 4. The imaging optical systemaccording to Example 4 consists of a first optical system G1, a secondoptical system G2, and a third optical system G3 in order from themagnification side to the reduction side. The first optical system G1consists of lenses L1 a to L1 n in order from the magnification side tothe reduction side. The second optical system G2 consists of lenses L2 ato L2 h in order from the magnification side to the reduction side. Thethird optical system G3 consists of lenses L3 a to L3 f, an aperturestop St, and lenses L3 g to L3 k in order from the magnification side tothe reduction side. A first intermediate image MI1 is formed between thefirst optical system G1 and the second optical system G2, and a secondintermediate image MI2 is formed between the second optical system G2and the third optical system G3.

Regarding the imaging optical system of Example 4, Tables 10A and 10Bshow basic lens data, Table 11 shows specification, Table 12 showsaspheric surface coefficients thereof, and FIG. 17 shows aberrationdiagrams. Table 10A, Table 10B, and FIG. 17 show data in a case wherethe distance from the magnification side imaging surface to the lenssurface closest to the magnification side is 752.7.

TABLE 10A Example 4 Sn R D Nd νd *1 −23.4002 5.6000 1.53158 55.08 *2−67.4066 2.9737 3 50.2132 1.8000 1.77250 49.60 4 21.1622 4.3629 530.5740 1.2500 1.84666 23.78 6 16.7031 4.5068 7 30.0574 1.1000 1.7725049.60 8 13.8399 14.0250 9 −21.2316 7.8883 1.48749 70.44 10 −72.80751.1582 11 −29.1761 7.9388 1.51742 52.43 12 −26.8894 2.4254 13 98.53622.4578 1.80518 25.45 14 −131.0927 13.6633 15 −274.1587 3.7214 1.7725049.60 16 −56.5163 30.2783 17 46.3619 12.8813 1.49700 81.54 18 −33.46511.3000 1.84666 23.78 19 −97.4449 6.8150 20 −254.1227 1.2500 1.8466623.78 21 31.8864 16.0184 1.49700 81.54 22 −43.1246 4.5068 *23 −45.74653.4000 1.51007 56.24 *24 −40.5167 31.1565 25 67.8839 10.7414 1.8051825.45 26 −256.5697 86.3175

TABLE 10B Example 4 Sn R D Nd νd 27 35.6505 4.4354 1.80610 33.27 28434.1509 13.5330 29 145.0938 1.0000 1.84666 23.78 30 16.9932 4.22891.48749 70.44 31 −48.4652 0.7719 32 33.3611 2.9569 1.80518 25.45 3371.0231 13.1476 34 −17.1088 1.0000 1.77250 49.60 35 27.3353 6.64741.49700 81.54 36 −21.5932 2.3361 37 120.6863 10.5218 1.49700 81.54 38−23.7460 5.6358 39 42.9176 4.5218 1.84666 23.78 40 109.5455 33.1011 41−20.7702 2.2073 1.76182 26.52 42 273.0566 1.4042 43 −476.8238 18.20641.80400 46.58 44 −33.3866 1.0686 45 256.8037 7.6457 1.80400 46.58 46−80.6379 38.0040 47 43.9334 6.4580 1.58913 61.13 48 −130.5795 6.9138 4925.2060 7.8524 1.80610 33.27 50 49.6192 1.0626 51 557.5986 3.00001.69895 30.13 52 11.7201 4.6807 53(St) ∞ 2.6807 54 −21.7843 3.01091.49700 81.54 55 −9.8082 1.9332 1.75520 27.51 56 −17.4515 5.0898 57332.8753 1.8851 1.59551 39.24 58 32.9615 9.6900 1.49700 81.54 59−19.4105 14.9786 60 60.8421 5.3043 1.80518 25.42 61 −241.8781 13.0006 62∞ 26.5000 1.51633 64.14 63 ∞ 0.0393

TABLE 11 Example 4 |f| 4.99 FNo. 2.40 2ω(°) 137.0

TABLE 12 Example 4 Sn 1 2 KA −9.257099336489E−01  −4.999990881777E+00 A31.985136918204E−03  2.385259309972E−03 A4 −9.578192696406E−05 −2.404768263625E−04 A5 1.615430177955E−06  1.733287951793E−05 A63.124939881493E−07 −2.842529868774E−07 A7 −2.887647319497E−08 −4.385675485220E−08 A8 5.107902220288E−10  1.383172920372E−09 A94.632774338826E−11  1.499498500746E−10 A10 −2.209061867475E−12 −8.812217716797E−12 A11 −1.345795100928E−14  −9.830322949355E−14 A122.683547704222E−15  1.723698034612E−14 A13 −3.099849783220E−17 −1.977208609514E−16 A14 −1.450454609593E−18  −1.495435830036E−17 A153.409823417801E−20  3.787207224236E−19 A16 2.756947013206E−22 4.931843191971E−21 A17 −1.364363093674E−23  −2.437393418552E−22 A184.129821538406E−26  6.670674082221E−25 A19 1.989627169765E−27 5.565234378128E−26 A20 −1.679492947259E−29  −5.576486086969E−28 Sn 2324 KA −1.598772035783E+00  −4.999992219558E+00  A3 0.000000000000E+000.000000000000E+00 A4 4.123953593132E−05 3.966469406399E−05 A52.150026343229E−06 1.722377142344E−06 A6 −2.897355240011E−07 −2.323836721419E−07  A7 −9.942402280972E−09  −6.268137348279E−10  A83.842042238064E−09 1.951943307926E−09 A9 −1.506297631693E−10 −5.030379238303E−11  A10 −1.509011702469E−11  −9.515825735045E−12  A111.056541347725E−12 2.763491459111E−13 A12 2.270120616023E−142.916285110467E−14 A13 −2.885638796700E−15  −8.294096726983E−16  A141.623687403355E−18 −5.208265921899E−17  A15 3.929917370535E−181.361275593330E−18 A16 −4.193482420055E−20  5.227627291260E−20 A17−2.647759191289E−21  −1.112433404036E−21  A18 4.302554608484E−23−2.750189344529E−23  A19 7.038183986554E−25 3.533591422182E−25 A20−1.384413304729E−26  5.954593142748E−27

FIG. 18 shows an example, in which the optical path is deflected, as amodification example of Example 4. The imaging optical system ofModification Example 4-1 shown in FIG. 18 is configured such that twooptical path deflecting members are added to the imaging optical systemof Example 4 so as to deflect the optical path twice. In the imagingoptical system of Modification 4-1, a first optical path deflectingmember R1, which deflects the optical path by 90 degrees, is disposedinside the first optical system G1, and a second optical path deflectingmember R2, which deflects the optical path by 90 degrees, is disposed tobe closest to the magnification side in the second optical system G2.

Table 13 shows corresponding values of Conditional Expressions (1) to(11) of the imaging optical systems of Examples 1 to 4, and Table 14shows numerical values relating to the conditional expressions. Examples1 to 4 use the d line as a reference wavelength, and Tables 13 and 14show values based on the d line.

TABLE 13 Expression Ex- Ex- Ex- Ex- Number ample 1 ample 2 ample 3 ample4 (1) |f1/f| 2.43 2.29 1.81 2.08 (2) |f12/f| 1.70 1.21 1.56 1.15 (3)|Bf/f| 6.95 7.04 6.51 6.11 (4) |Ymax/f| 2.27 2.27 2.60 2.60 (5) θ −8.87−7.32 9.56 12.44 (6) hdA 0.813 0.394 0.125 0.215 (7) hdB 0.162 0.1320.166 0.047 (8) (TL × Ymax)/ 40.7 39.3 46.4 38.5 (|h| × |f|) (9) (f1 ×Ymax²)/ 2.68 2.44 1.71 1.98 (|h| × f²) (10) |h1/dd1| 0.162 0.132 0.1660.215 (11) |h2/dd2| 0.813 0.394 0.125 0.047

TABLE 14 Example 1 Example 2 Example 3 Example 4 f1 27.482 20.770 9.00810.367 f12 −19.202 −10.996 −7.801 −5.718 Bf 78.670 63.740 32.471 30.482Ymax 25.70 20.56 13.00 13.00 h 52.98 43.91 35.81 35.62

As can be seen from the above data, the imaging optical systems ofExamples 1 to 4 each have a small F-number of 2.4 or less and ensures awide image angle of 130 degrees or more in all angles of view whilekeeping the lens diameter small. Each aberration is satisfactorilycorrected, thereby realizing high optical performance. Further, theimaging optical systems of Examples 1 to 4 each are able to use rays inthe entire area of the image circle including the vicinity of theoptical axis, and each are configured to be telecentric on the reductionside.

Next, a projection type display device according to an embodiment of thepresent disclosure will be described. FIG. 19 is a schematicconfiguration diagram of a projection type display device according toan embodiment of the present disclosure. The projection type displaydevice 100 shown in FIG. 19 has the imaging optical system 10 accordingto the embodiment of the present disclosure, a light source 15,transmissive display elements 11 a to 11 c as light valves eachcorresponding to each color light, dichroic mirrors 12 and 13 for colorseparation, a cross dichroic prism 14 for color synthesis, condenserlenses 16 a to 16 c, and total reflection mirrors 18 a to 18 c thatdeflect the optical path. In addition, FIG. 19 schematically shows theimaging optical system 10. Further, an integrator is disposed betweenthe light source 15 and the dichroic mirror 12, but is not shown in FIG.19.

White light originating from the light source 15 is separated into rayswith three colors (green light, blue light, and red light) through thedichroic mirrors 12 and 13. Thereafter, the rays respectively passthrough the condenser lenses 16 a to 16 c, are incident into andmodulated through the transmissive display elements 11 a to 11 crespectively corresponding to the rays with the respective colors, aresubjected to color synthesis through the cross dichroic prism 14, andare subsequently incident into the imaging optical system 10. Theimaging optical system 10 projects an optical image, which is formed bythe light modulated through the transmissive display elements 11 a to 11c, onto a screen 105.

FIG. 20 is a schematic configuration diagram of a projection typedisplay device according to another embodiment of the presentdisclosure. The projection type display device 200 shown in FIG. 20 hasa imaging optical system 210 according to the embodiment of the presentdisclosure, a light source 215, DMD elements 21 a to 21 c as lightvalves corresponding to respective color rays, total internal reflection(TIR) prisms 24 a to 24 c for color separation and color synthesis, anda polarization separating prism 25 that separates illumination light andprojection light. In addition, FIG. 20 schematically shows the imagingoptical system 210. Further, an integrator is disposed between the lightsource 215 and the polarization separating prism 25, but is not shown inFIG. 20.

White light originating from the light source 215 is reflected on areflective surface inside the polarization separating prism 25, and isseparated into rays with three colors (green light, blue light, and redlight) through the TIR prisms 24 a to 24 c. The separated rays with therespective colors are respectively incident into and modulated throughthe corresponding DMD elements 21 a to 21 c, travel through the TIRprisms 24 a to 24 c again in a reverse direction, are subjected to colorsynthesis, are subsequently transmitted through the polarizationseparating prism 25, and are incident into the imaging optical system210. The imaging optical system 210 projects an optical image, which isformed by the light modulated through the DMD elements 21 a to 21 c,onto a screen 205.

FIG. 21 is a schematic configuration diagram of a projection typedisplay device according to still another embodiment of the presentdisclosure. The projection type display device 300 shown in FIG. 21 hasan imaging optical system 310 according to the embodiment of the presentdisclosure, a light source 315, reflective display elements 31 a to 31 cas light valves each corresponding to each color light, dichroic mirrors32 and 33 for color separation, a cross dichroic prism 34 for colorsynthesis, a total reflection mirror 38 for deflecting the optical path,and polarization separating prisms 35 a to 35 c. In addition, FIG. 21schematically shows the imaging optical system 310. Further, anintegrator is disposed between the light source 315 and the dichroicmirror 32, but is not shown in FIG. 21.

White light originating from the light source 315 is separated into rayswith three colors (green light, blue light, and red light) through thedichroic mirrors 32 and 33. The separated rays with the respectivecolors respectively pass through the polarization separating prisms 35 ato 35 c, are incident into and modulated through the reflective displayelements 31 a to 31 c respectively corresponding to the rays with therespective colors, are subjected to color synthesis through the crossdichroic prism 34, and are subsequently incident into the imagingoptical system 310. The imaging optical system 310 projects an opticalimage, which is formed by the light modulated through the reflectivedisplay elements 31 a to 31 c, onto a screen 305.

FIGS. 22 and 23 are external views of a camera 400 which is the imagingapparatus according to the embodiment of the present disclosure. FIG. 22is a perspective view of the camera 400 viewed from the front side, andFIG. 23 is a perspective view of the camera 400 viewed from the rearside. The camera 400 is a single-lens digital camera on which aninterchangeable lens 48 is attachably and detachably mounted and whichhas no reflex finder. The interchangeable lens 48 is configured suchthat an imaging optical system 49 as the optical system according to theembodiment of the present disclosure is housed in a lens barrel.

The camera 400 comprises a camera body 41, and a shutter button 42 and apower button 43 are provided on an upper surface of the camera body 41.Further, operation units 44 and 45 and a display section 46 are providedon a rear surface of the camera body 41. The display section 46 displaysa picked-up image or an image within an angle of view before imaging.

An imaging aperture, through which light from an imaging target isincident, is provided at the center on the front surface of the camerabody 41. A mount 47 is provided at a position corresponding to theimaging aperture. The interchangeable lens 48 is mounted on the camerabody 41 with the mount 47 interposed therebetween.

In the camera body 41, there are provided an imaging element, a signalprocessing circuit, a recording medium, and the like. The imagingelement (not shown in the drawing) such as a charge coupled device (CCD)or a complementary metal oxide semiconductor (CMOS) outputs a picked-upimage signal based on a subject image which is formed through theinterchangeable lens 48. The signal processing circuit (not shown in thedrawing) generates an image through processing of the picked-up imagesignal which is output from the imaging element. The recording medium(not shown in the drawing) records the generated image. The camera 400captures a static image or a moving image by pressing the shutter button42, and records image data, which is obtained through imaging, in therecording medium.

The present disclosure has been hitherto described through embodimentsand examples, but the present disclosure is not limited to theabove-mentioned embodiments and examples, and may be modified intovarious forms. For example, values such as the radius of curvature, thesurface distance, the refractive index, the Abbe number, and theaspheric surface coefficient of each lens are not limited to the valuesshown in the numerical examples, and different values may be usedtherefor.

In addition, the projection type display device according to thetechnology of the present disclosure is not limited to the aboveconfiguration, and may be modified into various forms such as theoptical member used for ray separation or ray synthesis and the lightvalve. The light valve is not limited to a form in which light from alight source is spatially modulated through an image display element andis output as an optical image based on image data, but may be a form inwhich light itself output from the self-luminous image display elementis output as an optical image based on the image data. Examples of theself-luminous image display element include an image display element inwhich light emitting elements such as light emitting diodes (LED) ororganic light emitting diodes (OLED) are two-dimensionally arranged.

Further, the imaging apparatus according to the technology of thepresent disclosure is not limited to the above configuration, and may bemodified into various forms such as a camera other than a non-reflexsystem, a film camera, a video camera, and a camera for movie imaging.

What is claimed is:
 1. An imaging optical system in which amagnification side imaging surface and a reduction side imaging surfaceare conjugate, wherein the imaging optical system forms a firstintermediate image at a position conjugate to the magnification sideimaging surface and a second intermediate image at a position closer toa reduction side than the first intermediate image on an optical pathand conjugate to the first intermediate image, wherein the imagingoptical system consists of a first optical system, a second opticalsystem, and a third optical system in order from a magnification side tothe reduction side along the optical path, wherein magnification sidesurfaces of all lenses of the first optical system are located on theoptical path to be closer to the magnification side than the firstintermediate image, wherein magnification side surfaces of all lenses ofthe second optical system are located on the optical path to be closerto the reduction side than the first intermediate image and to be closerto the magnification side than the second intermediate image, whereinmagnification side surfaces of all lenses of the third optical systemare located on the optical path to be closer to the reduction side thanthe second intermediate image, and wherein the imaging optical systemdoes not include a reflective member having a power.
 2. The imagingoptical system according to claim 1, wherein assuming that a focallength of the first optical system is f1, a combined focal length of thefirst optical system and the second optical system is f12, and a focallength of the imaging optical system is f, Conditional Expressions (1)and (2) are satisfied, which are represented by1<|f1/f|<5  (1), and0.8<|f12/f|<3  (2).
 3. The imaging optical system according to claim 1,wherein assuming that a back focal length of the imaging optical systemon the reduction side is Bf, and a focal length of the imaging opticalsystem is f, Conditional Expression (3) is satisfied, which isrepresented by5<|Bf/f|  (3).
 4. The imaging optical system according to claim 1,wherein assuming that a maximum image height on the reduction sideimaging surface is Ymax, and a focal length of the imaging opticalsystem is f, Conditional Expression (4) is satisfied, which isrepresented by1.9<|Ymax/f|  (4).
 5. The imaging optical system according to claim 4,wherein in a case where a maximum image height on the reduction sideimaging surface is Ymax and a ray is incident from the reduction sideimaging surface to the imaging optical system at a height of Ymax froman optical axis in parallel with the optical axis, assuming that an airgap in which the first intermediate image is located is a first air gapin a case where the first intermediate image is located inside the airgap, and an air gap which is adjacent to the magnification side of alens in which the first intermediate image is located is the first airgap in a case where the first intermediate image is located inside thelens, an angle formed between a first extension line obtained byextending the ray in the first air gap and the optical axis is θ, and asign of θ is negative in a case where the first intersection point,which is an intersection point between a first extension line and theoptical axis, is located to be closer to the magnification side than thefirst intermediate image, and the sign of θ is positive in a case wherethe first intersection point is located to be closer to the reductionside than the first intermediate image, where a unit of θ is degrees,Conditional Expression (5) is satisfied, which is represented by−15<θ<15  (5).
 6. The imaging optical system according to claim 1,wherein in a case where a maximum image height on the reduction sideimaging surface is Ymax and a ray is incident from the reduction sideimaging surface to the imaging optical system at a height of Ymax froman optical axis in parallel with the optical axis, assuming that aheight of the ray from the optical axis on a lens surface closest to themagnification side in the second optical system is h1, an air gap inwhich the first intermediate image is located is a first air gap in acase where the first intermediate image is located inside the air gap,and an air gap which is adjacent to the magnification side of a lens inwhich the first intermediate image is located is the first air gap in acase where the first intermediate image is located inside the lens, anintersection point between a first extension line obtained by extendingthe ray in the first air gap and the optical axis is a firstintersection point, a distance on the optical axis between the firstintersection point and the lens surface closest to the magnificationside in the second optical system is dd1, a height of the ray from theoptical axis on a lens surface closest to the magnification side in thethird optical system is h2, an air gap in which the second intermediateimage is located is a second air gap in a case where the secondintermediate image is located inside the air gap, and an air gap whichis adjacent to the magnification side of a lens in which the secondintermediate image is located is the second air gap in a case where thesecond intermediate image is located inside the lens, an intersectionpoint between a second extension line obtained by extending the ray inthe second air gap and the optical axis is a second intersection point,a distance on the optical axis between the second intersection point andthe lens surface closest to the magnification side in the third opticalsystem is dd2, and a larger value of |h1/dd1| and |h2/dd2| is hdA and asmaller value of |h1/dd1| and |h2/dd2| is hdB, Conditional Expressions(6) and (7) are satisfied, which are represented by0.1<hdA<1  (6), and0.03<hdB<0.3  (7).
 7. The imaging optical system according to claim 1,wherein in the imaging optical system, an absolute value of a height ofa principal ray having a maximum angle of view from an optical axis isthe maximum on a lens surface closest to the magnification side in thefirst optical system, wherein assuming that a distance on the opticalaxis from the lens surface closest to the magnification side in theimaging optical system to a lens surface closest to the reduction sidein the imaging optical system is TL, a maximum image height on thereduction side imaging surface is Ymax, a height of the principal raywith the maximum angle of view from the optical axis on the lens surfaceclosest to the magnification side in the first optical system is h, anda focal length of the imaging optical system is f, ConditionalExpression (8) is satisfied, which is represented by20<(TL×Ymax)/(|h|×|f|)<60  (8).
 8. The imaging optical system accordingto claim 1, wherein assuming that a focal length of the first opticalsystem is f1, a maximum image height on the reduction side imagingsurface is Ymax, a height of the principal ray with the maximum angle ofview from the optical axis on the lens surface closest to themagnification side in the first optical system is h, and a focal lengthof the imaging optical system is f, Conditional Expression (9) issatisfied, which is represented by1.2<(f1×Ymax²)/(|h|×f ²)<4  (9).
 9. The imaging optical system accordingto claim 1, wherein all optical elements included in the imaging opticalsystem have a common optical axis.
 10. The imaging optical systemaccording to claim 1, further comprising two or more optical pathdeflecting members that deflect the optical path.
 11. The imagingoptical system according to claim 2, wherein Conditional Expression(1-1) is satisfied, which is represented by1.5<|f1/f|<3  (1-1).
 12. The imaging optical system according to claim2, wherein Conditional Expression (2-1) is satisfied, which isrepresented by1<|f12/f|<2  (2-1).
 13. The imaging optical system according to claim 3,wherein Conditional Expression (3-1) is satisfied, which is representedby6<|Bf/f|<20  (3-1).
 14. The imaging optical system according to claim 4,wherein Conditional Expression (4-1) is satisfied, which is representedby2.1<|Ymax/f|<3.2  (4-1).
 15. The imaging optical system according toclaim 5, wherein Conditional Expression (5-1) is satisfied, which isrepresented by−13<θ<13  (5-1).
 16. The imaging optical system according to claim 7,wherein Conditional Expression (8-1) is satisfied, which is representedby30<(TL×Ymax)/(|h|×|f|)<50  (8-1).
 17. The imaging optical systemaccording to claim 8, wherein Conditional Expression (9-1) is satisfied,which is represented by1.5<(f1×Ymax²)/(|h|×f ²)<3  (9-1).
 18. A projection type display devicecomprising: a light valve that outputs an optical image; and the imagingoptical system according to claim 1, wherein the imaging optical systemprojects the optical image, which is output from the light valve, on ascreen.
 19. An imaging apparatus comprising the imaging optical systemaccording to claim 1.